This invention is in the field of lyotropic liquid crystal (LLC) materials, in particular, cationic imidazolium surfactants that can form LLC phases when mixed with water or room temperature ionic liquids (RTILS) as the solvent. The imidazolium surfactants may be polymerizable.
Lyotropic liquid crystals (LLCs) are amphiphilic molecules (i.e., surfactants) containing one or more hydrophobic organic tails and a hydrophilic headgroup, that spontaneously organize in the presence of water or another polar solvent to form highly ordered yet fluid, phase-separated assemblies with periodic polar and non-polar domains on the 1-10 nm scale (FIG. 1) (Tiddy, G. J. T. Phys. Rep. 1980, 57, 1-46; Seddon, J. M. Biochim. Biophys. Acta 1990, 1031, 1). LLC phases include the normal hexagonal (HI) phase, the lamellar (L) phase, bicontinuous cubic (Q) phases, and the inverted hexagonal (HII) phase. FIG. 1 illustrates these phases for LLC mesogens with hydrophilic headgroups and hydrophobic organic tails in water or other polar solvent. As shown in FIG. 1, the HI phase has rod-like micelles arranged in a hexagonal array. The surface of the rod-like micelles is composed of the hydrophilic head groups of the LLCs, while the hydrophobic tails are isolated inside the micellar rods. The L (planar bilayer) phase in FIG. 1 has a double layer of molecules arranged so that the headgroups form the surface of the layer while the hydrophobic tails are isolated inside the layer. In the HII phase shown in FIG. 1, water-filled cylindrical channels are arranged in a hexagonal array. The hydrophilic headgroups surround the channels of water while the hydrophobic tails fill the volume between the channels of water. In the Q phases, channels or interconnected manifolds of water or other polar solvent are connected as a three-dimensional network surrounded by an organic bilayer of the LLCs. The hydrophilic headgroups of the amphiphiles surround the channels of polar solvent, or vice versa. These phases are termed bicontinuous because they have two or more unconnected but interpenetrating hydrophobic and/or aqueous or polar solvent networks with overall cubic symmetry. Depending on where they appear on the phase diagram relative to the central lamellar (Lα) phase, these Q phases can be classified as Type I (oil-in-water or normal) or Type II (water-in-oil or inverted). FIG. 2 illustrates two QI phases and two QII phases (both Ia3d and Pn3m) in which the interpenetrating organic networks (dark) are separated from one another by a continuous water layer surface (light) with overall cubic symmetry
When these LLC phases are successfully cross-linked, robust polymer materials with unique nanoporous architectures are generated (Mueller, A.; O'Brien, D. F. Chem. Rev. 2002, 102, 727; Miller, S. A.; Ding, J. H.; Gin, D. L. Curr. Opin. Colloid Interface Sci. 1999, 4, 338; O'Brien, D. F.; Armitage, B.; Benedicto, A.; Bennet, D. E.; Lamparski, H. G.; Lee, Y.-K.; Srisiri, W.; Sisson, T. M. Acc. Chem. Res. 1998, 31, 861-868), These nanoporous LLC polymer networks have been shown to be highly valuable as heterogeneous catalysts, molecular size-selective filtration membranes, and selective vapor barrier materials when water is used to form the LLC phases and in the hydrophilic channels (Gin, D. L.; Lu, X.; Nemade, P. R.; Pecinovsky, C. S.; Xu, Y.; Zhou, M. Adv. Funct. Mater. 2006, 16, 865878; Gin, D. L.; Gu, W.; Pindzola, B. A.; Zhou, W.-J. Acc. Chem. Res. 2001, 34, 973-980) Enhanced performance such as improved reactivity, selectivity, and/or transport of molecules can arise when reactions or transport occur in either the ordered nanostructured aqueous or hydrocarbon domains.
Recently, there has been a great deal of academic and industrial interest in room-temperature ionic liquid (RTILs), as well as in new polymer- and liquid crystal (LC)-based materials containing RTILs. RTILs are organic salts that are liquid at or below 100° C., and are composed entirely of cations and anions (i.e., free of any additional solvents) (Welton, T. Chem. Rev. 1999, 99, 2071-2083; Welton, T. Coord. Chem. Rev. 2004, 248, 2459-2477). They have attracted broad interest as novel solvents and liquid media for a number of applications because they have a unique combination of liquid properties. They have very low volatility, relatively low viscosity, high thermal stability, low flammability, high ionic conductivity, tunable polar salvation and transport properties, and in some cases, even catalytic properties. These characteristics have made RTILs excellent candidates as environmentally benign solvents to replace conventional organic solvents in many chemical, electrochemical, and physical extraction/separation processes In addition, RTILs have been shown to be novel gas separation media in supported liquid membranes (SLMs), (Scovazzo, P.; Visser, A. E.; Davis, J. H., Jr.; Rogers, R. D.; Koval, C. A.; DuBois, D. L.; Noble, R. D. “Supported Ionic Liquid Membranes and Facilitated Ionic Liquid Membranes,” ACS Symposium Series 818 (Ionic Liquids), 2002, 69-87; Schaefer, T.; Branco, L. C.; Fortunato, R.; Izak, P.; Rodrigues, C. M.; Afonso, C. A. M.; Crespo, J. G. “Opportunities for Membrane Separation Processes using Ionic Liquids,” ACS Symposium Series 902 (Ionic Liquids IIIB: Fundamentals, Progress, Challenges, and Opportunities), 2005, 97-110) and novel catalysts in a number of chemical processes (Welton, 1999, 2000), with performance enhancements in both cases due to the unique properties of RTILs.
One area of specific interest within the area of RTILs is the development of nanostructured polymer- and/or LC-derived RTIL materials. A collective goal of this latter work is the design of solid, immobilized RTIL materials and anisotropic gels with most of the desirable characteristics of RTILs, but without the mechanical limitations of a liquid (Ohno, H.; Yoshizawa, M.; Ogihara, W. Electrochim. Acta 2004, 50, 255-261). Most of the work in this latter area has centered around polymerizable RTILs (Washiro, S.; Yoshizawa, M.; Nakajima, H.; Ohno, H. Polymer 2004, 45, 1577-1582; Ohno, H.; Yoshizawa, M.; Ogihara, W. Electrochim. Acta 2004, 50, 255-261; Nakajima, H.; Ohno, H. Polymer 2005, 46, 11499-11504); RTIL-polymer composites (Carlin, R. T.; Fuller, J. Chem. Commun. 1997, 1345; Sneddon, P.; Cooper, A. I.; Scott, K.; Winterton, N.; Macromolecules 2003, 36, 4549-4556); surfactant LC-RTIL blends (Wang, L.; Chen, X.; Chai, Y.; Hao, J.; Sui, Z.; Zhuang, W.; Sun, Z. Chem. Commun. 2004, 2840-2841; Wang, Z.; Liu, F.; Gao, Y.; Zhuang, W.; Xu, L.; Han, B.; Li, G.; Zhang, G. Langmuir 2005, 21, 4931-4937); RTIL-derived LC systems (Bradley, A. E.; Hardacre, C.; Holbrey, J. D.; Johnston, S.; McMath, S. E. J.; Nieuwenhuyzen, M. Chem. Mater. 2002, 14, 629-635; Yoshio, M.; Mukai, T.; Kanie, K.; Yoshizawa, M.; Ohno, H.; Kato, T. Chem. Lett. 2002, 320-321; Firestone, M. A.; Dzielawa, J. A.; Zapol, P.; Curtiss, L. A.; Seifert, S.; Dietz, M. L. Langmuir 2002, 18, 7258-7260; Firestone, M. A.; Rickert, P. G.; Seifert, S.; Dietz, M. L. Inorg. Chim. Acta 2004, 357, 3991-3998; Yoshio, M.; Mukai, Ohno, H.; Kato, T. J. Am. Chem. Soc. 2004, 126, 994-995; Mukai, T.; Yoshio, M.; Kato, T.; Yoshizawa, M.; Ohno, H. Chem. Commun. 2005, 1333-1335; Binnemans, K. Chem. Rev. 2005, 105, 4148-4204); and most recently, polymerizable RTIL-based LC systems (Yoshio, M.; Kagata, T.; Hoshino, K.; Mukai, T.; Ohno, H.; Kato, T. J. Am. Chem. Soc. 2006, 128, 5570-5577). Most of these endeavors have been directed towards designing better solid-state ion conductors and anisotropic ion conductors for batteries and energy storage.
Prior RTIL-LC and RTIL-derived LC materials have been reported with 1-D columnar hexagonal and 2-D lamellar LC and LLC morphologies (Wang 2004; Wang 2005; Bradley 2002; Yoshio 2002; Firestone 2002, Firestone 2004; Yoshio 2004; Mukai 2005; Binnemans; 2005; Yoshio 2006). There is also a report of an RTIL-derived single-head/single-tail surfactant that formed a transient LLC phase with Q like character when mixed with water. However, the authors state in their paper that this LLC phase lacks the XRD peaks to support a Q phase and that it is better described as a hexagonal type phase with some cubic character (Firestone 2004).
A few examples of RTILs and polymerizable RTILs with two joined (i.e., gemini) imidazolium headgroups has been reported in the literature These systems include isotropic liquids for applications such as solvents and high-temperature lubricants (Anderson, J. L.; Ding, R.; Ellern, A.; Armstrong, D. W. J. Am. Chem. Soc. 2005, 127, 593-604; Jin, C.-M.; Ye, C.; Phillips, B. S.; Zabinski, J. S.; Liu, X.; Liu, W.; Schreeve, J. M. J. Mater. Chem. 2006, 16, 1529-1535); or precursors to non-ordered polymers (Nakajima, H.; Ohno, H. Polymer 2005, 46, 11499-11504).
Also, antibacterial bis(imidazolium quaternary salts) have been reported U.S. Pat. No. 3,853,907 to Edwards et al.
One of the most sought-after goals in the area of nanostructured RTIL-LC or polymer materials is the design and synthesis of Q-phase composites containing RTIL components, especially for ion conducting materials. Unfortunately, only a handful of polymerizable small molecule surfactants are known in the prior art that can be polymerized in Q phases (for examples, see Lee, Y.-S.; Yang, J.-Z.; Sisson, T. M.; Frankel, D. A.; Gleeson, J. T.; Aksay, E.; Keller, S. L.; Gruner, S. M.; O'Brien, D. F. J. Am. Chem. Soc. 1995, 117, 5573; Srisiri, W.; Benedicto, A.; O'Brien, D. F.; Trouard, T. P. Langmuir 1998, 14, 1921; Yang, D.; O'Brien, D. F.; Marder, S. R. J. Am. Chem. Soc. 2002, 124, 13388; Pindzola, B. A.; Jin, J.; Gin, D. L. J. Am. Chem. Soc. 2003, 125, 2940-2949). These exemplary Q-phase LLC monomer systems were designed to interface with and form Q-phases around water as the polar solvent, not RTILs.
Consequently, there remains a need for new surfactants and polymerizable surfactants that can form LLC phases with RTILs and other polar solvents to generate superior nanocomposite materials for enhanced application performance.